Electricity not wasted on cows

A new study suggests that some of the microorganisms found in cow waste may provide a reliable source of electricity.

Results showed that the microbes in about a half a litre of rumen fluid - fermented, liquefied feed extracted from the rumen, the largest chamber of a cow's stomach - produced about 600 millivolts of electricity. That's about half the voltage needed to run one rechargeable AA-sized battery, said Ann Christy, a study co-author and an associate professor of food, agricultural and biological engineering at Ohio State University in America.

While rumen fluid itself won't be used as an energy source, some of the microorganisms found in the fluid are also found in cow dung, which may prove to be a good source for generating electricity. In fact, in a related experiment, the researchers used cow manure directly to create energy for a fuel cell.

Using cow dung as an energy source isn't a new idea - some farmers already use the methane released by livestock waste to power machinery and lights. But converting methane into electricity requires costly equipment - one California farmer reportedly spent $280,000 to convert his operation to a methane digester system.

"Methane still needs to undergo combustion, which creates issues with energy efficiency," said Hamid Rismani-Yazdi, the study's lead author and a graduate student in food, agricultural and biological engineering at Ohio State.

The research showed how electricity can be created as the microorganisms in rumen fluid break down cellulose - a complex carbohydrate that is the primary component of the roughage that cows eat. That breakdown releases electrons.

This study represents the first time that scientists have used cellulose to help charge a fuel cell.